Re: Copper Banding?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>

Tesla list wrote:
> Original poster: Kurt Schraner <k.schraner@xxxxxxxxxxx>
> Hi David, Scott D,
> well, the effect is _real_, and not a matter of words only. Let me remind 
> a former posting, where a comparison of measured vs. calculated L values 
> has been shown, at:
> http://www.pupman.com/listarchives/2004/October/msg00018.html
> I didn't yet get an answer, explaining in easy to understand physical 
> reasoning, about the difference. Might be, it can be interpreted, by way 
> of a higher interturn capacitance in ribbon primaries, than "wire" spirals 
> of the same planar geometry, counteracting the inductance?
> Regards,
>           Kurt Schraner
> Tesla list schrieb:
>
> > Original poster: "david baehr" <dfb25@xxxxxxxxxxx>
> >
> > In a previouse post, it was stated that a banded pri. would have less 
> > inductance than a copper tubing pri. Could someone explain this ? IF YA 
> > got 50' of copper tubing , and 50' of banded pri. , wouldnt be about the 
> > same ????????////

The reason is that a flat spiral made with tape acts as a stack of coupled 
filamental coils. If the coupling were unitary, the inductance
would be the same of a single filament. But as the coupling between distant 
filaments is smaller than one, the inductance decreases.
Consider for example two parallel filamental coils with inductance L.
If they are at small distance, they act as a single coil with inductance
L. If they are far apart, the coupling between them is insignificant,
and the total inductance falls to L/2.

Antonio Carlos M. de Queiroz